Traditional antennae used on the exterior of an aircraft can simultaneously receive and transmit a plurality of RF signals. These traditional antennae and the aircraft on which they are installed are made of materials such as stainless steel, aluminum or other metallic materials. When an antenna receives or transmits two or more RF signals, an undesired mixed RF signal, which is a combination of RF signals sent to and from the antenna, is generated between the antenna and the aircraft. PIM occurs when the undesired RF signal's carrier falls within an antenna receiving RF band, and the undesired RF signal interferes with RF signals that are regularly sent to the antenna.
Therefore, there is a need to provide reduction of PIM when an aircraft is in flight condition.